Balanced demodulator



' April 24, 1951 G, L. FERNSLER 2,550,409 n BALANCED DEMODULATOR Filed Oct. 3, 1946 43 Sheets-Sheet 1 Gea/ye L. frfzsler El, g

tttorneg April 24, `1 951, G. L. FERNSLER 2,550,409

BALANCED DEMODULATOR Filed 001;. s, 194e s sheets-sheet 2 Gttornm April 24, 1951 G. FRNSLER 2,550,409

BALANCED DEMODULATOR Filed Oct. 3, 1946 3 Sheets-Sheet I5 Ihwentor Gttorneg Patented Apr. 24, 1951 BALANCE!) DEMODULATOR George L. Fernsler, Lawrenceyille, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application October 3, 1946, Serial No. 700,879 24 claims. (ci. 25o-2o) This invention relates to coupling systems for balanced modulator 4and ,demodulator systems and particularly relates'to demodulator systems suited f or use in frequency-modulated ultra highf-frequency systems such as lused for object location, height determination, .and similar purposes.

In general, theuse of balanced demodulators is of material advantage at ultra ,hghdrequencies vsuchas three thousand megacycles and higher,

because aording an enhanced signal-to-noise ratio not `attainable at these frequencies `by the useuof preamplication. ;They are also of advantage in minimizing lor precluding radiation from the antenna of the output of the local oscil-.

liator used for heterodyning received energy;

this is of importance in avoidance ofY interference to other nearby receivers and of betrayal of the presence or location of the receiver.

In accordance with the invention, the signal 'from one source, specically a receiving antenna,

line sections to produce elds therein affording :in-phase or out-of-phase response of the demodulators respectively associated therewith in dependence upon their poling and. coupling. The

latter `pair of resonant cavities are also coupled to aV second source of ultra high-frequency energy, specifically a local oscillator, for production of eldsl therein which` are applied in-phase or out-of-phase to the demodulators; this second source through the coupling afforded by the aforesaid slots, loops, or probes produces elds in theV iirst cavity which, however, mutually cancel.,

The invention also resides in features of construction, combination and arrangement herein disclosed and claimed. Y

` For a more ,detailed understanding of the invention and for illustration of various forms thereof, reference is made tothe accompanying drawings, in which: Y Figure 1 in perspective, partly broken away, shows a balanced rdemodulator utilizing three Awave-guide sections;

Figure 2 is a sectional View taken on the broken line v2 4. of Figure 1; f

Vclosed-ended waveguide sections.

Figure Z-A is a schematic plan view of the cavity structure of Figure 1;

Figure 3 is a circuit diagram showing a preferred output circuit for the demodulators of Figures 1 and 3;

Figure 4 is a sectional View on enlargedl scalel .oi one of the demodulator units of Figure l;

Figure 5 comprises explanatory curves referred to in discussion of Figures 1-3;

Figures 6-9 inclusive are sectional views of other modifications of the invention;

Figure 10 is a sectional View of still another modification; and

Figures 11 and l2 are sectional views taken respectively on lines II-II and I2-I2 of Figure 10.

Peferring to Figure 1, the antenna I0 or other y Source of ultra-high-frequency energy is connected by transmission line II, which may be a wave guide or coaxial line, to the resonant cavity I2 which is a closed-ended section of a wave guide, the electrical length of which is 4-I-N quarter wavelengths, where N is zero or any even integer. There are thus produced, within the cavity I2, electric and electromagnetic fields having nodes and anti-nodes at definitely fixed positions axially of the cavity. Curve A of Figure 5 represents, at a particular instant, the electric held as a function of axial distance of the cavity: at a time interval corresponding with a halfcycle earlier or later, the curve A is inverted, the location of the nodes remaining at the ends and intermediate half-wave points.`

A second source I3 of ultra-high-frequency energy, for example a local oscillator, is conv nected, preferably by a lossy concentric line I4,

to two resonant cavities I5 and I6 which, in this modication of the invention, are also two The electrical length of each of the cavities I 5 and I6 is selected or adjustedV to be wavelengths long, where M is zero or any even integer. -There are thus produced, Within each of cavities I5 and it, electric and electromagnetic elds having nodes and anti-nodes at fixed positions axially of it. Curves B and C of Figure 5 represent the electric elds in cavities I5 and I6 respectively each as a function'of distance along the axis of the cavity. With the cavities similarly excited from corersponding ends, the fields vary in phase; at a time interval corresponding with a half-cycle earlier or later, both curves B line I I extending to the antenna It. because of the relations above stated, there is and C are inverted from the full line position shown with nodes at the ends and the half-wave point or points.

Preferably, and as indicated in Figure 2-A, each of the three cavities is tunable by a plunger il adjustable externally of the cavity by a rod I8 or equivalent.

The cavity I2 is coupled to the cavities t5 and I6 by slots, loops, or probes so positioned with respect to the electric or electromagnetic fields wtihin the cavity I2 that the energies they transfer to cavities I5 and i5 are 180 out of phase.

In the particular arrangement shown, the transfer is effected by the probes I9 and 2t, Figure 2A, entering cavity I2 from opposite side walls thereof and spaced from each other axially of the cavity I?. by Q quarter wavelengths where Q is an even integer: furthermore, the electrical length of the cavity between each of the probes and the near closed end of the cavity is an odd number of quarter wavelengths. Referring to curve A, Figure 5, one of the probes, for example probe 2U, may be positioned at the point AI or point A3 along one side wall of the cavity I2 .and the otherYV probe I9 may be positioned at point A2 along the opposite side wall of the cavity. In Figure 2A, the cavity I2 is a wave-length long and the probes are in positions corresponding with AI and A2, Figure 5.

The wavelengths thus far mentioned in connection with the length of cavity i2 .and the spacing of the probes I9 and 2l! are in terms of frequency FI of source IE! and as measured' with- "in the guide, not as measured in free space.

With respect to cavities i5 and i6, the probes I9 and 2B enter them at such points that with respect to the fields therein produced by the source .i3 each tends to produce in the cavity I2 an electric or electromagnetic field Iwhose standing wave pattern is the opposite of that produced by the other probes. Hence, there is little or no energy of frequency F2 of oscillator I3 transmitted through the resonant cavities to the transmission Conversely,

little or no` transfer of energy of frequency FI through the resonant cavities to the transmission line Ill.

It is to be further noted that each of the r shielded probes I9 and 20 enters the respective "cavity i5 or I5 at a point which is an odd number .of the tuning plungers will be approximately the same.

By way of example, for frequencies of about 3000 megacycles (l cm.) ,each of the wave-guide sections i2, l and I6 may have internal dimensions 20 cm. x 7 cm. x 1.27 cm., the extra internal l length allowing tuning from about 10 cm. to about '12 cm. and permitting reasonable length of the tuning plunger. The wave-guide sections need `.not be of rectangular cross section though that configuration is preferred because it is simpler to Ypredict the field patterns and possibility of excitation of the cavities at undesired modes is avoided. The .arrangement specifically shown and described aords mechanical and electrical simplicity 'in obtaining the desired phase relations above disclosed. y

In attainment of the proper relative positions of the probes and for matching of impedances, the cavities l5 and It may be adjusted toward or away from the center cavity I2, Figure 2, to vary the extent to which the probes extend into the electrical fields of they cavities and further, each of the cavities I5 and IS may be moved lengthwise of and parallel to the center of cavity ,r-

IZ so that the inner ends of the probes I9 and 26 are at points of desired or maximum difference of potential of the electric field therein. When loops or slots are used as coupling means,

a generally similar arrangement should be pro-Y vided for adjustment of the coupling and of the phasing. Y

The demodulators 2l and 22, Figure 3, respectively associated with the outer cavities I6 and i5 are suitably coupled to the fields therein by loops or probes. In the particular arrangement shown, the coupling is to the electro-magnetic fields and is effected by loops so located and oriented that with respect to the fields of frequency FI produced within the cavities by the aforesaid coupling to cavity I2 their outputs may be out-of-phase but are in-phase with respect to the fields of frequency F2 produced within the cavities I5 and I6 by the aforesaid coupling to the oscillator I3 or equivalent.

Specifically, the loop 23 which enters the left face of cavity I6 (Fig. 1) at a point or region which is a selected or adjusted to be about a quarter wavelength from the near closed end of the cavity, is connected (Fig. 3) to one terminal of rectifier 2|, a diode or crystal rectifier of the .selenium or equivalent metallic type, whose other terminal is connected to one terminal of coupling impedance I3 through a filter network comprising series resistor 24 and parallel capacitors 25, and designed to attenuate the frequencies FI and F2. The loop 25 which enters the cavity I5 (Fig. l) through the right-hand face at the corresponding regicn of cavity I5, or a region which is an even number of quarter wavelengths from said region, is connected (Fig. 3) to one terminal of rectifier 22 whose other terminal is connected to wall structure of the cavity through the filter network comprising the parallel capacitors 28 and parallel resistor 29, and designed to attenuate the frequencies FI and F2. The other terminal of loop 26 is effectively connected by bypass cond-enser 27 to the cavity so far as frequencies FI and F2 are concerned and for the modulation or demodulation frequencies is conductively connected to the other or lower terminal of the impedance 73. Coupling to an intermediate or audio-frequency amplifier is effected by the output impedance 30 and coupling capacitor 3 I. By adjustment of the movable contact of the impedance 73 either push-pull or push-push op.

eration may be attained.

A preferred physical construction of the arrangement for coupling the demodulator 22 to the cavity I5 is shown in Figure 4. The legs of the U-shaped member forming the loop 26 slidably receive the conductors 32 and 33 to form a tunable section of a parallel-conductor transmission line whose fields are confined by the metal sleeve or tube 34 suitably held against or attached to the youter wall of cavity I5. The inner sleeve 3.5 which slidably and rotatably engages the outer` tube 34 serves as an extension of the shield for the line 32-33 and as a support for a plug of insulation in which is mounted a metallic insert forming a holder for the crystal rectifier 22. The distributed capacity between this insert 'andthe ale-swine 5 sleevel 35 'forii'i's one 'of the filter capacitors 28; 'the` distributed capacity between the sleeve 35 Mand fa second'inse'rt for the conductor 33 forms the' bypass capacitor 2'I.` The unit comprising sleev'e35 in'ay be withdrawn for adjustment of the eLectricalI l'en'gth `of the line comprising loop 26 and c'nd'uct'ors 32, 33 to a half Wavelength or other even number f :quarter wavelengths. With the 'unitin place it may be adjusted axially of fthe tube 34 to vary the coupling to cavity I5 and so attain the 'desired matching in compensation y Aforv differences 4between theimpedances of different crystals.

The outer face of lengthwise to allow adjustment o-f the demodulator unit for coupling to the desired region ,within the cavity: in suchcase the slot is covered bya slidable metallic plate, except at region of entry of the coupling loop.

'A rgc-inerally similar arrangement is used for couplingthe rectifier 2l to cavity I5 except, as apparent Afrom Figure 3, the line conductorwhich doesA not include the crystal rectifier 2| is conductively connected to the shell 35.

With the external connections of the sources tothe cavities as shown in Figure 1, noise in the oscillator output is balanced out so to improve the `ratio of the-received signal to noise produced within the receiver: by interchanging the sources I and I3, amplitude modulation in the received Asignal maybe balanced out. t

A All of the modifications subsequently described,

the cavity I 5 may be slotted l x thoughdiffering specifically from each other and vfrom `the, form of thel invention shown in Figures 1 4, are alike in fundamentalfeatures of cony struction Aand operation; consequently for brevity the corresponding elements of the various lmodifications are in general'identied by like reference characters differing only in suffix and theremainder of the description is principally directed to significant differences o-f construction or arrangement. In general, vthe modications using closed-end coaxial lines for all three resonant cavities are more practical for ultra highy frequencies up to about 4000 megacycles whereas Vthose using Wave guide sections fory all three cavities are more practical for frequencies from about 4000 megacyclesto possibly 30,000 lmegacycles. In the range of from about v30004 megacycles to about 4000 megacy'cles, the combination of coupled4 cavities may include both types of kresonant cavities. ,I t

vIn the modification shown in Figure 6, the cavity IZA is'a closed section of "coaxial line whose vinner conductor is dividedy to form a YU-shaped loop having legs 36 extending from the closed end `3'! of the loop whichis presented Yto the lefthand or yclosed end'of the'cavity. The legs r36 of fthe loop 'sli'dably receiveY the conductors' 38 and V39,'whichform 'continuations thereof and extend respectively Vto form the inner conductors ofthe sinaller concentric lines ISA and I5A. By design or adjustment the 'impedance of Veach of the lines' I5Afan"d vIIiA is 'one-half the impedance of the line IZA, softo effect an impedance match at the junction of the lines. The loop 40A connected by a balanced transmission line IIA to the source I0 is symmetrically disposed within the cavity IZA in inductive relation to the loop 3I so that the energiestransferred from the source vminor-reflector disc or plate 4l'.

match` at the antenna end of the line IIB is loop 3l so that so far as the second source I3 is concerned, the energies transmitted therefrom by the line I2A to the lines I5A and ISA are in phase.

The sleeve 4I, the conductors 38 and 39, and 'the `lines I5A and IGAQare adjustable as aV unit 'for tuning of theV cavity or line I2A. 'Io obtain equality of the reactances of the lines I5A and vIIA as seenby the cavity IZA, provision is made to adjust the electrical lengths of one or both of the lines 15A or IBA. For exampley as shown, the sleeve 42 and conductor 43 move as a unit and form a telescoping extension of the conductors of the line I5A. In general, this modification is similar to that of Figure 1 except that the desired v vv|213. and is effectively balanced by the quarter- The overlap of the loops Wave cavity choke 44. B and 3GB-31B is about one-half wavelength and the electrical Vlength of cavity I2B between its junction with lines IAB and its junction with'lines 15B and IISB is an odd number 'of quarter wavelengths, preferably not greater than five.` Balance at the antenna end of the line `I IB is effected by a similar choke 45 positioned between the -rnain reflector' Vill-and the dipole antenna elements 46 respectively connected to the inner and outer conductors o-f the line IIB, which is terminatedat its antenna end by the An impedance effected by the-adjustable stub line 49 vassociated with a wide-banding transformer 50 symmetrical with, respect to the stub 49.

' A similar arrangement comp-rising the adjustfable stub 5| and wide-banding transformer 52 is provided inthe input line I ziB between the cavity I2B and the second source of ultra-high-frequency energy, which may be an yoscillator Iprovided with a resonant cavity 53.

. -I-n this modification, the matching and b'alancing of the impedances of the concentric lines I5B and ISB are effected by the tuning stub and broad-band transformer arrangements 55, 51 and H54, 56 respectively. By way of example, the transformer sections 50, 52, 56 and 5l may eachv 'be one half wavelength long and the associated wherein VZ1---iin'pedance of the transformer section 20L-impedance of the stub Sectio-n ZA=impedance of the line The length of each of the stubs is preferably adjustable to facilitate matching or rematcln'ngr. The broad-band action for an assumed load impdanee;such as that'o'f crystal recunerzl of 22,

is adaptable to rematching by adjustmento the corresponding stub 54 or 55 in compensation for reasonable deviations from the assumed value.

Ooupling of the rectifiers 2| and 22 to the associated amplifier tube 6I may be effected by transformer 58 tuned to resonance by condenser 59 and damped by resistor 60 for suitable broadening of its` resonance characteristic to encompass the desired modulation band.

In the modification shown in Figure 8, as in that of Figure 6, energy from source Il] is introduced into the cavity I2C by a loop 40C formed by a continuation kof the inner conductor of the balanced transmission line IIC. The rectiers 2IC and 22C disposed respectively in the smaller lines I5C and IBC are diodes, known as McNally tubes, designed for enclosure in a concentric line. Because of construction of the tubes, it is necessary to connect the cathodes together or use separate power supplies for their heaters. The latter arrangement is chosen for use of the unit,

Figure l8, as a balanced detector or demodulator. The modification shown in Figure 9 is similar to that of Figure 1 in that the resonant input cavity connected to source I is of the wave-guide type and is similar to the modifications shown in Figures 6-8 in that the demodulator cavities ID and ISD are of the concentric-line type. The energy from source I0 may be introduced into the cavity I2D in any suitable manner, for example by concentric line IID whose inner conductor forms a loop within the cavity. The resonant frequency of cavity I2D may be varied by adjustment of the tuning plug I'ID or equivalent. As in the modifications of Figures 6-8, the inner conductors 36D of the lines AI5D and IBD are joined to form a loop 31D whose electrical midpoint is connected to the inner conductor of the transmission line extending from the second source I3 of ultra-high-frequency energy. The energies to lines ISD and IBD from source I3 are, therefore, in phase. frequency FI at opposite sides of the cylindrical cavity I2D are 180 out of phase, the energies of that frequency picked up by loop 31D and delivered to lines I5D and IBD are out of phase. The length of at least one of lines I5D, IBD may be adjustable in manner and for reasons discussed in connection with Figure 6.

In the modification shown in Figures -12, the resonant cavities I5E and ISE are semi-cylindrical and have a common partition or wall 64 with a central slot. Theradius of each of the cavities is selected for resonance at the desired frequency: for example, for frequencies corresponding with wavelengths of about 7 centimeters the radius may be about 2.62 centimeters. Tuning is effected by adjustment of plugs I'IE or equivalent. A continuation of the inner conductor 65 of the line IIE from source I0 excites the cavities in push-pull relation. Matching of the line I2E formed by conductor 65 and wall structure is provided for by the tuning stubs` 66 and 1I, the former in alignment with transmission IIE and extending from the oppositeA face of the cavity structure. The tuning plungers of these stubs are adjusted to provide a current anti-anode or conductor 65 midway of its length between the opposite faces of the cavity structure. The cavities ISE and ISE are excited in push-push relation from source I3 by the loops 69 and 'I0 formed by extensions of the inner conductors of two coaxial lines 68 branched from the transmission line I4E. Matching is provided by the stub SIE: alternatively, each of lines 68 may be provided with a stub.

However, as the fields ofr fin ifs

ated with said pair of cavities for in-phase reelectrical length is Coupling to each of the rectifiers 2I and 22, which may be crystals or diodes, is effected by a conductor l2, Figure 12, extending across the corresponding cavity from one terminal of the rectifier to the opposite side of the cavity. Foi matching, the conductor 'I2 forms the inner conductor of a stub 6l whose adjustable plunger determines the effective electrical length of the stub.

As in all modifications previously herein described, although both signal sources are coupled to the demodulators the coupling between the sources are balanced out; also, the noise or amplitude modulation undesirably present in one of the signals is balanced out so that it does not to substantial extent appear in the joint output of the demodulators.

Although all the coupling arrangements disclosed have been described as utilized for balanced demodulation systems, they are adaptable for use in balanced modulation systems as well. This involves change in sense of the transfer of the modulation-frequency energy, that is, the rectifiers are in a supply circuit rather than a load circuit; moreover, the antenna circuit becomes a load circuit rather than a signal source so far as the coupling arrangement is concerned. With these differences in mind, however, the adaption of the various arrangements for use in balanced modulator systems particularly suited for operation at ultra high frequencies should be evident to those skilled in the art. v

It shall be understood the invention is not specifically limited to the particular embodiments I shown but that changes and modifications may be made within the scope of the appended claims.

I claim as my invention:

1. A balanced ultra-high-frequency demodulator comprising a resonant cavity, a source of ultra high frequency coupled to said cavity to produce a field therein, a pair of resonant cavities provided with rectifier devices and respectivelyV coupled to said first-named cavity at regions in said first-named cavity where the field energies are in phase opposition and a second source of ultra high frequency coupled to each of said pair of cavities to produce in said pair of cavities fields which are in phase and to produce in said firstnamed cavity, by its aforesaid coupling with said pair of cavities, fields which mutually cancel.

v2. A balanced ultra-high-frequency demodulator comprising two sources of ultra high frequency, a closed wave-guide section coupled to one of said sources, a pair of wave-guide sections, means coupling said pair of sections to said first-named section at regions where the variations of the eld produced by said one of said sources are in phase opposition, means coupling the other of said sources to said pair of sections to produce therein in-phase fields which through said first-named coupling means produce mutually cancelling fields in said rstnamed section, and demodulating means associsponse to fields therein due to one of said sources and for out-of -phase response to fields therein due to the other of said sources.

3. A coupling system comprising a cavity whose wavelengths where n is zero or an even integer, two rectifier cavities each having an electrical length of wavelengths, and means for effecting coupling between each of the rectifier cavities and the firstnamedcavity at regions. each an odd number of quarter wavelengths from an end of the corresponding cavity, said regions of the first-named cavity being spaced from one another by an even number of quarter wavelengths.

V4. A balanced ultra-high-frequency demodulator system .comprising a'n input cavity whose electrical length is wavelengthswhere l71. is zero or an even integer, meansV for introducing received ultra-high-frequency energy into said cavity, two demodulator cavities each having an electrical length of wavelengths, a local oscillator for similarly exciting said demodulator cavities, and means for effecting coupling between each of the demodulator cavities and the input cavity at regions each an odd number of quarter wavelengths from an end fof the corresponding cavity, said regions of the input cavity being spaced from one another by au even number of quarter wavelengths.

5. A balanced ultra-high-frequency coupling system comprising threerclosed resonantcavities arranged side by sida-means for introducing ultra-high-frequency energy into the intermediate cavity, and means for effecting transfer of ultra-high-frequency energy from said intermediate cavity at regions spaced from each other an even number of quarter wavelengths longitudinally thereof to the outer cavities respectively.

6. A balanced ultra-high-frequency coupling `ducing into the intermediate cavity energy whose frequency substantially corresponds with the resonant frequency of that cavity, means for introducing into the outer cavities, at corresponding regions thereof and in phase, energy whose frequency substantially corresponds with their resonant frequency, and means for effecting couplingbctween regions of the intermediate cavity which. are spaced longitudinally from each other by anv even number of quarter wavelengths and regions of the outer cavities each spaced from the nearer end of the corresponding outer cavity by an odd number of quarter wavelengths.

8. A balanced ultra-high-frequency coupling system comprising three wave-guide sections arranged side by side, eld-coupling means between the intermediate section and each of the outer sections, and means for adjusting each of the outer sections in directions longitudinally and transversely of the intermediate section to obtain desired phasing and impedance matching.

9. A balanced ultra-high-frequency demodulator comprising a pair of coaxial lines Whose inner conductors extend beyond the open ends of the lines and are joined to form a loop, a resonant cavity whose outer conductor forms a continuation of the outer conductors of said lines and within which said loop is enclosed, demodulators in the closed ends of said lines, a source of signal energy connected to the closed end of said loop and to said outer conductor for in-phase response of said demodulators, a second source of signal energy, and means coupling said second source to said cavity to produce therein an electromagnetic iield which through said loop eiects out-of-phase response of said demodulators.

10. A balanced ultra-high-frequency demodulator comprising a coaxial-line section open at one end and whose inner conductor is divided forming a loop having its open ends directed toward the open end of said line, a source of ultra high frequency connected to the closed end of said loop and to the outer conductor of said line,

second source of ultra high frequency inductively coupled to said loop, a pair of coaxial lines extending from the open end of said line section with their inner conductors forming extensions of the open ends of said loop and their outer conductors jointly closing the open end of said section, the impedances of said lines being equal and substantially half the impedance of said section. and demodulators in said coaxial lines for inphase response to one of said sources and out-oi phase response to the other of said sources.

1l. A balanced ultra-high-frequency demodulator comprising a pair of coaxial lines whose Y outer conductors are the continuation of the outer conductor of a larger'line and whose inner conductors are joined to form a loop in said larger line, means adjustable to eiect a match between the impedance of the larger line and the joint impedance of said pair of lines, demodulators in said pair of lines, means adjustable to effect equality of the surge impedances of said pair of lines, a sources of ultra mgh frequency inductiveiy coupled to said loop, and a second source of high frequency connected between the midpoint of said loop and a point on the outer conductor.

l2. A coupling system for a balanced ultrahigh-frequency demodulator or modulator cornprising a pair or" coaxial lines whose outer conductors merge to form the cuter conductor of a larger line and whose inner conductors are `joined to form a loop in said larger line, the closed end of said loop and the adjacent portion of said larger outer conductor being adjustable in unison for matching of the impedance of the larger line to the resultant of the impedances of said pair of lines, and rectifiers in said pair of lines.

13. A. coupling system for a balancedultrahigh-frequency demodulator or modulator com-- prising a pair of coaxial lines whose. outer conductors merge to form the outer conductor of a larger line and whose inner-conductors are joined to form a loop in said larger line, the

.f closed end of said loop and the adjacent portion of said larger outer conductor being adjustable in unison for matching of the impedance of the larger line tc the resultant of the impedances of said pair of lines, rectiers in said pair of lines, and means for varying the effective length of at least one of said pair of lines to balance the impedances or" said pair of lines.

le. A coupling system for a balanced ultrahigh-irequency demodulator or modulator comprising a pair of coaxial lines whose outer conductors form the continuation of the outer conductor of a resonant cavity and Whose inner conductors are joined Within said cavity to form a loop, rectifiers in said pair of lines, a matching stub for at least one of said lines to effect equality of their impedances as seen at the junction with said cavity, an input line connected to the closed end of said loop and to said outer conductor, and a second input line terminating Within said cavity in a loop coupled to said firstnamed loop.

15. A balanced ultra-high-frequency coupling system comprising a pair of resonant cavities coupled by a slot, a concentric line whose outer conductor terminates at said cavities and Whose inner conductor extends along said slot for inphase excitation of or by said cavities, and a second concentric line whose outer conductor terminates at said cavities and whose inner conductor forms loops in said cavities for out-ofphase excitation of o1' by said cavities.

16. A balanced ultra-high-frequency demodulator comprising a pair of resonant cavities coupled by a slot, two sources of ultra high frequency, a concentric line from one of said sources and whose outer conductor terminates at said cavities and Whose inner conductor extends along said slot for in-phase excitation of said cavities, a second concentric line from the other of said sources and whose outer conductor terminates at said cavities and whose inner conductor forms loops in said cavities to effect outof-phase excitation thereof, means for matching the impedances of said cavities, and means for matching the impedances of said lines to the joint impedances of said cavities.

17. A balanced ultra-high-frequency coupling system comprising cavity structure including a pair of resonant cavities coupled by a slot in their common Wall structure, a concentric line whose outer conductor terminates at said cavity structure and Whose inner conductor extends Within said slot for in-phase exchange of energy with respect to said cavities, and a second concentric line whose outer conductor terminates at said cavity structure and whose inner conductor forms loops respectively disposed in said cavities for in-phase exchange of energy.

18. A balanced ultra-high-frequency device as in claim 1 in which each of the three resonant cavities is a closed-ended section of waveguide.

19. A balanced ultra-high-frequency device as in claim 1 in which the resonant cavities for the rectier devices are each a coaxial line Whose inner conductor joins the inner conductor of the other line to form a loop Within the first-named resonant cavity of claim 1.

20. A balanced ultra-high-frequency device as in claim 1 in which the resonant cavities for the rectifier devices are each a coaxial line whose inner conductor is extended for joining the inner conductor of the other line to form a D Within the first-named resonant cavity of claim 1 and in which said first-named resonant cavity is a. coaxial line whose cuter conductor is a continuation of the outer conductors of the aforementioned coaxial lines and whose inner conductor is divided and joins the extensions of the aforesaid inner conductors thereof in formation of said loop. Y

21. A balanced ultra-high-frequency device as in claim 1 in which the resonant cavities for the rectifier devices are each in coaxial line whose inner conductor joins the inner conductor of the other line to form a first loop Within the firstnamed resonant cavity of claim 1 and in which a second loop Within said rst-n-amed cavity couples it to the first-named ultra-high-frequency source of claim `1;

22. A balanced ultra-high-frequency device as in claim 1 in which the resonant cavities for the rectifier devices are each a Vcoaxial line whose inner conductor joins the inner conductor of the other line to form a rlrst loop within the rstnamed resonant cavity of claim 1 and in which the first-named ultra-high-frequency source of claim l is coupled to the rst-narned cavity thereof and to the aforesaid coaxial lines by a second loop overlapping the aforesaid first loop.

23. A balanced ultra-high-frequency device as in claim 1 in which the resonant cavities for the rectifier devices are each a coaxial line Whose inner conductor joins the inner conductor of the other line to form a rst loop within the rstnamed resonant cavity of claim 1 and in which a second loop within said :first-named cavity is connected to the rst-named ultra-high-frequency source of claim 1 by a balanced transmission line.

24. A balanced ultra-high-frequency device as in claim 1 in which the resonant cavities for the rectier devices are each a coaxial line whose inner conductor joins the `inner conductor of the other line to form a loop within the first-named resonant cavity of claim 1 and in which said first-named resonant cavity is a close-ended section of Wave-guide which is a continuation of the outer conductors of said coaxial lines.

GEORGE L. FERNSLER.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS 

